Canon imageCLASS LBP6780dn - Protective Function; Failure Detection

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Technology > Fixing System > Fixing control circuit > Failure detection
Technology > Fixing System > Fixing control circuit > Failure detection
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Protective function
The protective function detects an abnormal temperature rise of the xing unit and interrupts
power supply to the xing heater.
The following three protective components prevent an abnormal temperature rise of the xing
heater:
• DC controller
• Fixing heater safety circuit
• Thermoswitch
1) DC controller
The DC controller interrupts power supply to the xing heater when it detects an abnormal
temperature of the xing heater.
2) Fixing heater safety circuit
The xing heater safety circuit interrupts power supply to the xing heater when the
detected temperature of the main and sub thermistors is abnormal.
3) Thermoswitch
The contact of the thermoswitch is broken to interrupt power supply to the xing heater
when the thermoswitch detects an abnormal temperature of the xing heater.
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Failure detection
The DC controller determines a xing unit failure, deactivates the FIXING HEATER
CONTROL signal,releases the relay to interrupt power supply to the xing heater and noties
the formatter of a failure state when it encounters the following conditions:
1) Start-up failure
• If the main thermistor does not detect a specied temperature during the start-up process
of the heater in the wait period.
• If the main thermistor does not detect a specied temperature during the heater
temperature control in the initial rotation period.
2) Abnormal low temperature
• If the main thermistor detects an abnormal low temperature of the xing unit during the
printing operation.
• If the sub thermistor detects an abnormal low temperature of the xing unit during the
printing operation.
3) Abnormal high temperature
• If the main thermistor detects an abnormal high temperature of the xing unit.
• If the sub thermistor detects an abnormal high temperature of the xing unit.
4) Frequency detection circuit failure
• If a specied frequency of the ZERO CROSSING signal is not detected within a specied
period after the printer is turned on.